Curvilinear LED light source

ABSTRACT

An LED system that simulates bare or exposed neon in appearance. The curvilinear LED light source comprises a rigid, formable light guide having a generally circular cross-section and a flexible LED light engine. The light guide is made of a material or materials that can be heated and formed into a desired shape. The light guide retains the desired shape upon cooling. The flexible light engine is inserted into a groove in the light engine.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to illuminated signs and artwork,particularly the invention relates to LED illuminated signs and artworkthat simulate neon signs.

2. Summary of Related Art

Currently, advertising and other signs are made of neon light bulbs,incandescent light bulb and/or fluorescent light bulbs. However, thereare many drawbacks to these prior art solutions. Incandescent andflourescent lights burn out easily. While neon lights have a longservice life, neon lights have several significant drawbacks. Neonlights are not durable and impact resistant. The tubes can break or bedamaged relatively easily, especially during shipping and handling. Neonlights are relatively difficult to install due to their high voltagerequirements. Neon lights are not easy to service. An entire sign mustbe removed form the site, taken back to the shop where it is eitherrepaired or replaced. Then the sign must be returned to and re-installedat the site. Neon signs contain mercury and rare gases that could posesenvironmental health and safety issues. Neon's high voltage requirementsmake compliance to strict regulatory requirements and national and localelectrical codes a major concern for sign companies and their customers.

Neon signs are created by heating a glass tube into a pliable state andbending it into the desired shape. The bent tube is injected with neonor another inert gas such as argon or a mercury argon mix. Neon givesoff a reddish orange color when it is excited and argon/mercury givesoff a blue color when it is excited. To create additional colors, theinside of the glass tube is coated with flourescent powders that absorblight in a given wavelength(s) and re-emit light in a differentwavelength.

In the past, attempts have been made to use LEDs as a substitute forneon lights. However, prior art LED solutions have been found to beunsatisfactory. Prior LED solutions can not be easily formed andmaintained into a desired shape by the sign companies. Custom shapesmust be ordered from the factory for higher prices and require longlead-times. Prior LED solutions do not offer a wide viewing angle. Awide viewing angle, greater than 180°, is more similar to neon lightsand is required for many applications. Prior art flexible LED solutionscan not make and hold tight bends or require special clips or customchannels to maintain a desired shape. Further, prior art LED solutionsare not generally the same size and shape as the neon tubes they aretrying to replace.

SUMMARY OF THE INVENTION

The present invention is an LED system that simulates bare or exposedneon in appearance and performance. The system is comprised of aformable light guide and a flexible light engine. The light guide has agenerally circular cross-section with a groove along its length. Thelight guide is made of a material or materials that can be heated andformed into a desired shape and retain the desired shape upon coolingwithout losing the original properties of the material. A flexible lightengine is then inserted into and retained by the groove along the lengthof the formed light guide. Different colors are acheived by usingdifferent light engines with the same light guide, different LEDs, ordifferent coatings.

The system produces a uniform lit appearance with a wide viewing angleand intensity similar to neon.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 a is a perspective view of the light guide.

FIG. 1 b is a perspective view of the LED light engine.

FIG. 2 is a cross section of one embodiment of the present invention.

FIG. 3 is a cross section of an alternative embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

In a first embodiment of the present invention, the light pipe 20 is arigid but formable rod 32 having generally circular cross-section.Preferably, rod 32 is comprised of multiple layers of material withdifferent optical properties. The base material 22 is preferablyoptically clear with good transmission. The base material 22 ispreferably extruded. A second layer, preferably comprising a diffusingmaterial 24, covers the base material 22. Second layer 24 is preferablycoated on the base material via co-extrusion, over-molding or cast, orother plastic processing means. Diffusing layer 24 can be varied insize, shape, thickness, and surface structure to achieve differentdesired effects such as viewing angle, uniformity, and intensity.Preferrably, there is a layer of optically clear material 62 over theoptically diffuse layer.

It is desirable that the layers of materials 22, 24 have similarphysical properties. It is preferably that the layers have similar glasstransition temperatures. This allows the rod 32 to be shaped via heatingwithout inducing high stresses in disimilar layers or between layers. Itis also preferably that the layers have similar coefficients of thermalexpansion. This allows for proper functioning of rod 32 throughtemperature cycles without losing structural integrity. The layers alsopreferably have similar indexes of refraction to minimize the losesassociated with light traveling from one medium to another.

The effect of diffuse layer 24 immersed on optically clear layer 22 isto simulate the appearance of gas inside a glass tube or the insidesurface of a glowing neon tube. Rod 32 could optionally be made entirelyof a optically diffuse material to achieve a uniform glow.

Rod 32 preferably has a groove 30 along the entire length. Preferablygroove 30 is adapted to retain a flexible LED light engine 50 when LEDlight engine 50 is inserted in groove 30. The specific shape of thegroove can be designed to mate features on flexible LED light engine 50to provide a frictional-fit or a snap-fit between rod 32 and flexibleLED light engine 50. Groove 30 also positions the flexible LED lightengine 50 in the proper location and orientation to achieve desirableresults with respect to viewing angle, uniformity, and intensity of theilluminated light guide.

Preferably, the light engine is sized similiarly to a neon tube.

In a first alternative embodiment, flexible LED light engine 50 iscomprised of at least one LED 54 mounted on each of a plurality ofcircuit boards 64 that are connected via wire jumpers 66. Alternatively,flexible LED light engine 50 comprises at least one LED mounted to aflexible circuit. In another alternative embodiment, flexible LED lightengine 50 comprises at least one LED 54 mounted to circuit board andinsert into a connector that is attached to a multi-wire bus. In yetanother alternative embodiment, flexible LED light engine 50 comprisesat least one LED 54 mounted to a leadframe. Preferably, the light enginecomprises a plurality of LEDs 54 connected in series/parallel, parallel,or parallel/series by wires 76. In another embodiment, flexible LEDlight engine 50 is co-extruded into a continuous profile of flexiblethermoplastic material 74. It is preferable that the flexiblethermoplastic have properties similar to layers 22, 24 of light guide20.

Optionaly, small sections of LED light engine 50 can be overmolded witha low melt temperature, thermoplastic 72 to provide weather resistance.The overmold could provide a retention/locking element to interact withgroove 30 in light guide 20. Thermoplastic 72 needs to have a melttemperature low enough to not damage the LEDs. Thermoplastic 72 can beeither flexible, ductile, or rigid. Preferably, thermoplastic 72 isclear and has an index of refraction that is similar to that of theepoxy used to mount the LEDs and that of light guide 20 to minimizelosses.

Light engine(s) 50 could operate on either a constant current orconstant voltage.

In an alternative embodiment, light guide 120 is a back lit light pipe132 formed around a mandrel 156 that has a generally circular crosssection and illuminated along its length via a flexible LED light engine150 with opposing LEDs 54 at each location or every other location thatemit light directed toward the edge of light pipe 132. LEDs 54 arepreferrably side-emitting LEDs. Forward emitting LEDs that are directedinto the edge of light pipe 150 can also be used. Total internalreflection (TIR) is utilized to direct the emitted light through lightpipe 132 around the circumference of the generally circular shape andradially outward from light pipe 132 to achieve a uniform lightappearance of the light guide around the circumference. This occurs ateach LED location along flexible LED light engine 150. Preferably, LEDs154 are spaced to achieve the desired uniformity along the length oflight pipe 150.

In another alternative embodimient, a layer of material that containsone or more phosphur is included in the light guide to achieve customcolors. The phosphur preferably can be excited by either blue or UVLEDs. Preferrably, the phosphur is a mono-, bi-, or tri-phosphur blend.Phosphur layer may be created by adding phosphur to the opticallydiffuse layer of material 24 or be a separate layer 80.

In another embodimient, flexible LED light engine could be comprised ofa multi-wire electrical bus with power and signal conductors with LEDsof different or the same color to achieve desired visual effects such aschasing, color changing, or dynamic color control.

In another embodiment, LED light engine could be co-extruded in centerof light guide with LEDs facing in opposing directions to achieve a 360°viewing angle.

In another embodiement, multiple LEDs per location aimed in differentdirections are used to increase viewing angle.

In another embodiment, additional LEDs are aimed in the oppositedirection of the light guide to provide back directed light output for ahalo effect.

A user such as a sign manufacturer thermoforms the rod 32 into a desiredshape using commonly available tools or equipment such as a PVC heatingblanket, a heat gun, or a PVC heating box (not shown). This forming canbe done either in a factory or at the site of installation. Afterheating the rod to a specific softening temperature or glass transitiontemperation, it can be either free formed or placed in a template of thedesired shape. Upon cooling the rod will retain the desired shape aswell as the original cross-sectional shape and material properties.Flexible LED light engine 50 of the desired color or colors is theninserted into and retained in groove 30 along the length of the formedrod 32. Alternatively, more than one light engine can be used. Thesystem is then mounted and connected to a low voltage power supply viasimple electrical connections.

Preferably, the curvilinear LED light source has a viewing angle of 180°or greater. Most preferably, the light has a viewing angle of about360°.

1. A curvilinear LED light source comprising: a light guide and at leastone LED light engine, wherein said light guide is adapted to be formedinto a desired shape, wherein the light guide comprises a rod with agroove extending longitudinally, said rod comprising of at least oneoptically difuse, layer and said groove adapted to retain said lightengine.
 2. The curvilinear LED light source of claim 1, wherein thelight guide is rigid.
 3. The curvilinear LED light source of claim 1,wherein the light guide is cabable of being formed when it is heated andretains a formed shape after it is cooled.
 4. The curvilinear LED lightsource of claim 1 wherein the light guide further comprises an opticallyclear base layer and said optically diffuse layer coats said base layer.5. The curvilinear LED light source of claim 1 wherein the light guidefurther comprises an optically clear outer layer that coats saidoptically diffuse layer.
 6. The curvilinear LED light source of claim 4further comprising a phosphur layer.
 7. The curvilinear LED light sourceof claim 6 wherein the diffusing layer is the phosphur layer.
 8. Thecurvilinear LED light source of claim 4 wherein the diffuse layercomprises a phosphur material.
 9. The curvilinear LED light source ofclaim 6 wherein the phosphur layer contains one or more phosphur or is amono-, bi- or tri-phosphur blend.
 10. The curvilinear LED light sourceof claim 6 wherein the phospur layer is excited by blue or by UV LEDs.11. The curvilinear LED light source of claim 4 wherein the layers havesimilar optical properties, the optical properties are selected from thegroup consisting of glass transition temperature, coefficients ofthermal expansion, indexes of refraction, and combinations thereof. 12.The curvilinear LED light source of claim 5 wherein the layers havesimilar optical properties, the optical properties are selected from thegroup consisting of glass transition temperature, coefficients ofthermal expansion, indexes of refraction, and combinations thereof. 13.The curvilinear LED light source of claim 1 wherein the light enginecomprises a plurality of LEDs.
 14. The curvilinear LED light source ofclaim 13 wherein the LEDs are spaced to achieve an overlapping beampattern resulting in a uniform light distribution along the length ofthe light rod.
 15. The curvilinear LED light source of claim 13 whereinthe LEDs are mounted on at least one pcb, a flexible circuit, a flexiblewire bus or combinations thereof.
 16. The curvilinear LED light sourceof claim 15 wherein the LEDs are mounted on at least two pcbs and thepcbs are conntected via wire jumpers.
 17. The curvilinear LED lightsource of claim 15 wherein the LEDs are connected to at least two pcbsand the pcbs are connected via wire jumpers and wherein the pcbs areinserted into a connector attached to a multi-wire bus.
 18. Thecurvilinear LED light source of claim 13 wherein the LED light enginecomprises a continuous profile of thermoplastic material or a siliconebased material
 19. The curvilinear LED light source of claim 13 whereinat least a portion of the LED light engine is overmolded with a lowmelt, thermoplastic material or a siliconce based material.
 20. Thecurvilinear LED light source of claim 3 wherein the base layer comprisesan elastomeric material, a silicoln based material, a thermoplasticmaterial or a combination thereof.
 21. The curvilinear LED light engineof claim 1 further comprising a low voltage power supply.
 22. Thecurvilinear LED light source of claim 1 wherein the light source has aviewing angle of greater than 180°.
 23. The curvilinear LED light sourceof claim 1 wherein the light guide comprises a elongated solid core rodwith a backlight light guide layer over the solid core.
 24. Thecuriviinear LED light source of claim 23 wherein the light guide has agenerally circular shape and total internal reflection (TIR) is utilizedto direct light emitted by the LED light engine through the light guidesuch that the light is emitted radially outward from light guide. 25.The curvilinear LED light source of claim 24 wherein the light enginecomprises at least two side emitting LEDs and said at least two sideemitting LEDs emit light in opposing directions.
 26. The curvilinear LEDlight source of claim 25 wherein the LEDs are spaced to achieveoverlapping beam patterns resulting in a uniform light distributionalong the length of the rod.
 27. The curvilinear LED light source ofclaim 25 further comprising a phosphur layer.
 28. The curvilinear LEDlight source of claim 27 the diffuse layer comprises a phosphurmaterial.
 29. The curvilinear LED light source of claim 27 wherein thephosphur layer contains one or more phosphur or is a mono-, bi- ortri-phosphor blend.
 30. The curvilinear LED light source of claim 27wherein the phospur layer is excited by blue or by UV LEDs.
 31. Thecurvilinear LED light source of claim 24 wherein the light enginecomprises a plurality of LEDs.
 32. The curvilinear LED light source ofclaim 31 wherein the LEDs are spaced to achieve overlapping beampatterns resulting in a uniform light distribution along the length ofthe light rod.
 33. The curvilinear LED light source of claim 31 whereinthe LEDs are mounted on at least one pcb, a flexible circuit, a flexiblewire bus or combinations thereof.
 34. The curvilinear LED light sourceof claim 33 wherein the LEDs are mounted on at least two pcbs and thepcbs are conntected via wire jumpers.
 35. The curvilinear LED lightsource of claim 33 wherein the LEDs are conntected to at least two pcbsand the pcbs are connected via wire jumpers wherein the pcbs areinserted into a connector attached to a multi-wire bus.
 36. Thecurvilinear LED light source of claim 31 wherein the LED light enginecomprises a continuous profile of thermoplastic material.
 37. Thecurvilinear LED light source of claim 23 wherein the core comprises anelastomeric material, a silicoln based material, a thermoplasticmaterial or a combination thereof.
 38. The curvilinear LED light sourceof claim 31 wherein at least a portion of the LED light engine isovermolded with a low melt, thermoplastic material.
 39. The curvilinearLED light engine of claim 26 further comprising a low voltage powersupply.
 40. The curvilinear LED light source of claim 24 wherein thelight source has a viewing angle of greater than 180°.
 41. A system forcreating an illuminated sign comprising the steps of: obtaining a lightguide; heating the light guide; shaping the heated light guide to adesired shape; cooling the light guide; attaching at least one flexibleLED light engine to the shaped light guide; and connect the light engineto a low voltage power supply.
 42. A method for building a curvilinearLED light source comprising the steps of co-extruding an LED lightengine in the center of an extruded light guide, said LED light engineshaving LEDs facing in opposing directions.